$color1: yellowgreen;

@mixin p1 {
    height: 50px;
    color: blue;
    background-color: #000;
}

;

#app {
    .container {
        color: red;
        background-color: $color1;

        p {
            @include p1;

            &:hover {
                font-size: 25px;
                background-color: skyblue;
            }
        }
    }
}